Dynamics of pulse signal forming from distal zones of radial arteries


Ye. Storchun, A. Klymukh

Lviv Polytechnic National University

In last time new methods and hardware-software system, which combine eastern medicine traditions and western technologies are commonly used in diagnostic practice. Pulse diagnostics is one of the ancient methods for disease state identification. For diagnostic purposes different kind of arteries zones can be observed, but most popular is pulse diagnostics of wrist joints radial arteries. It is based on recording of signal from three zones, lied closely along the radial arteries of left and right hands. For the purpose of pulse diagnostics special kinds of sensing devices are used.
Preliminary model with schema included acoustic impedances of artery part, soft tissues of registration zone and sensing device was proposed. In this model was assumed, that sensor occlusion force distributed between the model elements and other object structures is constant. Acoustic impedances of artery part and soft tissues were modeled by elastic component taking into consideration pulse signals spectrum. In this work modeling and experimental results of pulse signal forming by distal zone of radial artery depending on sensor occlusion force were presented.
Artery stiffness was defined from the curve showing dependency between the transmural pressure and the relative change of artery volume. Stiffness evaluation results were approximated by second order polynom relative to force conformed to diastolic pressure of patient. Experimental verification of new model for vessels with small tensibility was carried out. Data were obtained for artery zone length 5 mm and pulse pressure mmHg. Artery stiffness polynomial model took into consideration fraction of occlusion force fitted the artery and soft tissues .Initial data for modeling were  diastolic and pulse pressure of patient, artery diameter and length, and coefficient defining the increment of soft tissues impedance component depending on occlusive force.
All dependencies were evaluated for each patient in dependency of arterial blood pressure, artery diameter and elastic response. During the simulation study artery diameter was changed in range (1,9 – 3,8) mm in compliance with measuring results obtained by another authors. Length of artery registration zone was changed until the matching of computation and experimental results. Experiment was done using the device with piezoelectric and tensoresistive sensors joined mechanical sequentially.
Investigations for pulse signals from seven zones accordingly to eastern medicine canons were done for 4 patients in age 18-25 years old. Their results showed the adequacy of calculated meanings of pulse signal for different artery zone length in range of small values of occlusion forces. This fact can be explained by model affixment to the object exactly in this range. It can be suggested, that there is no interference of different zones during the pulse signal forming, when occlusive forces of sensors have value from range 0 – 2.0 N. In case of higher occlusive force values deformation of artery is starting. Consequences of deformation are that the elastic properties and pulse wave propagation process are changing. In such conditions process of pulse signal forming could not be described by elaborated model.